Eric Agol , Stuart Wyithe, Barbara Jones, Omer Blaes, Chris Fluke, PASA, 18 (2), in press.
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Title/Abstract Page: Mid-Infrared Imaging of the
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Motivation
The spectral-energy distributions of quasi-stellar objects (QSOs) generally show a change in spectral slope near 1 micron, which is indicative that a different emission mechanism operates longward of this wavelength. The spectrum typically peaks at 10-100 microns; the origin of this infrared bump is still in question. One candidate mechanism is thermal dust emission by dust surrounding the QSO which absorbs and reradiates the QSO light. The evidence is the constancy in wavelength of the dip near 1 micron (Neugebauer et al. 1987, Sanders et al. 1989), which may be attributed to the dust sublimation temperature, 
K. In a few Seyfert 1 galaxies (the nearby, lower- luminosity nieces of QSOs), reverberation studies between the optical and infrared indicate that the infrared lags the dust by several light months, which supports the dust model (Barvainis 1992, Nelson 1996). An alternative model is emission by self-absorbed synchrotron radiation from electrons. The evidence in favor of synchrotron emission is the lack of silicate features which are expected from dust emission and the in-phase infrared/optical variability in some radio-quiet QSOs, which indicates the optical and infrared emission regions are not distinct (Neugebauer & Matthews 1999).
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Title/Abstract Page: Mid-Infrared Imaging of the
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